A "Blue" Shift of Optical Absorption Bands of Single-Wall Nanotubes Grown from C:BN Mixtures by Arc-Discharge Techniqueстатья
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Аннотация:The electron and phonon properties of single-wall nanotubes synthesized from C:BN mixtures by arc-discharge technique have been analyzed. The BN content was varied from 0 to 50 weight%. The direct measurements of the absorption spectra of hetero-tubes obtained were performed for the suspensions of individual single-wall nanotubes in 1%-SDBS/D2O solution. The main optical absorption bands E(11)(sem), E(22)(sem), E(11)(met) ... were shifted toward the "blue" part of the spectrum while the BN content was increased in the initial mixture used for synthesis. Under all BN contents (0-50%) the typical features of carbon single-wall nanotubes were observed in the Raman spectra of heterotubes grown. No significant changes in G-mode (at 1592 cm(-1)) have been detected. In a low-frequency range a position of the dominating Raman breathing mode showed a "blue shift" while the BN content in the initial mixture increased. This was interpreted as an evidence of the bandgap increase in C:BN heterotubes. The "blue" shift of the optical absorption bands (about 140 nm) has been ascribed to the effect of incorporation of B and N atoms or BN clusters into the graphitic lattice of the nanotube wall. This led to the bandgap enlarge.